This invention relates to the measuring and setting of the crushing gap in crushers, such as gyrating disc or cone crushers.
At present, the crushing gap is ascertained by leading. In the leading process, the crusher is stopped, and a lead body is dropped into the gap on a string. When the crusher is restarted, the lead is deformed to a thickness equal to the crushing gap. If the gap so ascertained is incorrect, it is necessary to reset it, and then to perform the leading process again to check the setting. The leading process may have to be performed over and over again until an acceptable gap is measured.
This unsophisticated, trial-and-error process has obvious drawbacks. For instance, it implementation leads to considerable downtime and the final result may still not be accurate. Also, it is not uncommon for the operator to neglect to do his checks at the required frequent intervals, with the result that the gap is often too great as wear of the crusher takes place. This in turn means that the rock is not crushed to the required size and may have to be returned for a further pass, and attendant reduced production and efficiency. Even more serious in the case of diamond-bearing rock is the fact that diamonds can be lost if the gap is too great.
Experiments conducted by the inventor revealed that the power drawn by a gyradisc crusher during operation is not constant, even if other operating parameters, such as ore feed rate and ore size, are kept constant, but exhibits considerable variations. Furthermore, it was found that the amplitude of the variations is greater if the crushing gap is small than if the crushing gap is larger.
It is an object of the invention to use these findings in the measuring and setting of the crusher's crushing gap.